1. Field of the Invention
The present invention concerns streptavidin or avidin conjugated large unilammelar liposomes.
2. Background Information
The potential use of liposomes as carriers for the cell-specific delivery of macromolecules, the recognition mediated by specific cell surface markers, has attracted much interest in recent years (G. Gregoriadis, "Use of Monoclonal Antibodies and Liposomes to Improve Drug Delivery. Present Status and Future Implications", Drugs, 24, 261-266, (1982); D. Papahadjopoulos, T. Heath, F. Martin, R. Fraley and R. Straubinger, "Development of Liposomes as an Efficient Carrier System: New Methodology for Cell Targeting and Intracellular Delivery of Drugs and DNA", Targeting of Drugs, (G. Gregoriadis, J. Senior and A. Trouet, eds), pp. 375-391. Plenum Press, New York, (1982); E. Mayhew and D. Papahadjopoulos, "Therapeutic Applications of Liposomes", Liposomes, (M. J. Ostro, ed.), pp. 289-341, Marcell Dekker, New York, (1983); J. N. Weinstein and L. D. Leserman, "Liposomes as Drug Carriers in Cancer Chemotherapy", Pharmacol. Ther., 24, 207-233, (1984)).
Such targeted delivery systems should prove advantageous for drug delivery and gene transfer as they would permit directed incorporation of selected macromolecules into the appropriate cell type, while avoiding side effects due to nonspecific interactions with other cell types. Several groups have studied cell-specific delivery of liposomal contents using model in vitro culture systems. The general approach used in most of these studies has involved immunologically based targeting systems, and has relied on the availability of monoclonal antibodies that recognize histocompatibility antigens, or of antisera obtained against cell type-specific surface proteins In contrast, targeting of liposomes via ligand-receptor interactions has received less attention, although low density lipoproteins (V. O. Ivanov, S. N. Preobrazhensky, V. P. Tsibulsky, V. R. Babaev, V. S. Repin and V. N. Smirnov, "Liposome Uptake by Cultured Macrophages Mediated by Modified Low-Density Lipoproteins", Biochem. Biophys. Acta, 846, 76-84, (1985)) and insulin (A. G. Gitman, A. Graessmann and A. Loyter, "Targeting of Loaded Sendai Virus Envelopes by Covalently Attached Insulin Molecules to Virus Receptor-Depleted Cells: Fusion-Mediated Microinjection of Ricin A and Simian Virus 40 DNA", Proc. Natl. Acad. Sci. U. S. A., 82, 7309-7313, (1985)) have been utilized in this manner.
Applicants have previously demonstrated that the polypeptide hormone beta-nerve growth factor (NGF) can be chemically modified by biotinylation via its carboxyl groups (C-bio-NGF) without loss of binding activity for specific NGF receptors on rat PC12 pheochromocytoma cells (M. B. Rosenberg, E. Hawrot and X. O. Breakefield, "Receptor Binding Activities of Biotinylated Derivatives of Beta-Nerve Growth Factor", J. Neurochem, 46, 641-648, (1986)). In addition, C-bio-NGF is fully active in promoting neurite outgrowth from PC12 cells. Further, C-bio-NGF was shown to mediate the specific binding of the biotin-binding protein, streptavidin, to these cells, but not to a variant line of PC12 cells lacking NGF receptors.
Heretofore procedures for coupling proteins, such as streptavidin,, to the outer surface of liposomes have generally used disulfide bond linkages. Such linkages may not be very stable in vivo. David L. Urdal and Sen-itiroh Hakomori, "Tumor-associated Ganglio-N-triosylceramide", The Journal of Biological Chemistry, Vol. 255, No. 21, 10509-10516 (1980) describe reductive amination to link avidin to liposomes.
Liposomes and their potential use for delivering medicines is described by M. J. Ostro, "Liposomes", Scientific American, January, 1987, pp. 103 to 111.